Subretinal Neovascularization (SRN) is a pathologic lesion associated with diseases which cause blindness, such as macular degeneration. A primate model of SRN has been perfected and its natural history has been studied in detail. It is proposed to study the early stages of the model SRN in detail with several morphologic methods. Light and electron microscopy, HRP tracer studies and thymidine uptake studies will be used to reveal the morphologic features which distinguish lesions that form SRN from lesions that do not. These studies will involve serial sectioning and computer assisted analysis of SRN vessels. The data will pertain to several hypotheses concerning the pathogenesis of SRN and will provide the basis for a rational approach to its treatment. An effective method of delivery of drugs to the subretinal space has been developed in rabbits. The method, involving chronic cannulation of the vitreous and an implanted mini-pump, will undergo extensive tests in rabbits to determine distribution of substances within the eye and in monkeys to determine tolerance to the cannula. This method will be used to deliver steroids to model SRN lesions over a 3 week period to evaluate the inflammatory component of SRN pathogenesis. Eventually the drug delivery system will be used to measure angiogenic substances for their screen effect on the SRN. Finally, the role of choroidal ischemia in the pathogenesis of model SRN will be evaluated in monkeys. Transient choroidal ischemia will be produced by posterior ciliary artery ligation performed at various times before and after laser photocoagulation producing SRN.